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| Home > Publications database > Kalibration simulierter Temperaturgeschichten von Sedimentgesteinen |
| Book/Report | FZJ-2018-06661 |
1994
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/20153
Report No.: Juel-2909
Abstract: One of the major problems in simulating the spatial and temporal evolution of a sedimentary basin is the reconstruction and calibration (comparison of measured and calculated data) of the temperature history. In order to improve the calibration of simulated temperature histories several parameters were investigated with respect to their applicability for the calibration of temperature histories among them different maturity parameters like the vitrinite reflectance. As no organic maturity parameter can be converted directly into paleotemperatures other paleothermometers like fluid inclusions and fission tracks in apatite were investigated and the results were then integrated and used in the reconstruction of the temperature histories in four wells from the North-West German Basin using a ID forward modelling software. Two wells are situated in a part of the basin, where heating rates during the whole geological evolution were relatively low and the maximum burial is achived recently. On the contrary in the area of the other two wells in the western part of the lower Saxony Basin the thermal regime was strongly influenced by deep-seated intrusions which caused high heating rates during the Mid-Cretaceous. The intrusion of magmatic bodies subsequently was followed by the inversion of the basin. The determination of maturity with several different maturity indicators led to relative satisfactory maturity trends in all wells, only if samples which reveal different organic facies or strong impregnations with migrated hydrocarbons were excluded. Although the wells were subjected to different heating rates no shift of the maturity parameters with respect to vitrinite reflectance was observed. This indicates that a certain value of a maturity parameter reflects always the same maturity in terms of vitrinite reflectance. This observation has been made also for all so-called biomarker maturity parameters. This indicates that all organic maturity parameters evolve according to very similar reaction kinetics. A more or less detailed study of the diagenisis in the investigated sandstones and the determination of paleotemperatures in fluid inclusions and with AFTA (Apatite-Fission-Track analysis) gave indications especially on the maximum temperatures achived during the burial history of the studied sedimentary sequences. In one well it was flLrther possible to establish a paleothermal "gradient", which was much higher than the present gradient and which could also be related to the intrusion of the Bramscher Massiv. The timespan of maximum temperatures was constrained by AFTA. By integrating all paleotemperature values and the organic maturity parameters the burial - and temperature histories of the wells were reconstructed utilizing a 1-D forward modelling simulation programme. In this context different approaches to calculate vitrinite reflectance values were tested. The study shows that approaches based on reaction kinetics to calculate vitrinte reflectance are superior to approaches which are more empirical like the TII (Time-Temperature-Integral). The results of this study indicate clearly that without the help of paleogeothermometers which are sensible to maximum temperatures a satisfactory calibration of simulated temperature histories is hardly to perform. Only the integration of several parameters allows a more reliable reconstruction of temperature histories which is the key element for the reconstruction of oil- and gas generation. Fluid inclusions and AFTA are in this context the most promising tools in combination with organic maturity parameters. It should be emphazised that apart from the temperature history reconstruction, the availability of very accurate kinetic parameters for the calculation of oil- and gas generation is indispensable.
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